Broadband double-ridge waveguide magic tee

ABSTRACT

A broadband double-ridge waveguide magic tee employing two rods for connecting the upper ridge of the H-arm of the magic tee to both ridges of the E-arm of the magic tee. The upper ridges of each of the colinear side arms is connected to the nearest ridge of the E-arm. The lower ridges of the colinear side arms and the H-arm are connected to each other.

United States Patent inventors Appl. No. Filed Patented Assignee BROADBAND DOUBLE-RIDGE WAVEGUIDE MAGIC TEE ABSTRACT: A broadband double-ridge waveguide magic tee 6 Claims, 3 Drawing Figs. employing two rods for connecting the upper ridge of the H- us. or 333/11 magic 4865 magic 333/98 tee. The upper ridges of each of the colinear side arms is con- Int 3 5/12 nected to the nearest ridge of the E-arm. The lower ridges of Field 0iswlil..IIIIQIIIILIIIIIIIIIIIIIIIIIIIIIIIIIIIII 333/11 Side and connected to each Wieslaw Wojciech Siekanowicz; [56] Robert Wayne Paglione, both of Trenton,

References Cited UNITED STATES PATENTS 55 057 3,315,183 4/1967 Bunn et al.... 9

July 15,1970 3,383,630 5/1968 Kuroda Dec. 21, 1971 Primary Examiner-Herman Karl Saalbach RCA Corporation Assistant Examiner-Paul L. Gensler Atmmey-Edward J. Norton other.

PATENTEU 05:21 :97:

.EllmlllllL illllll Wwslaw W Sz'ekanawz'cz m m Z J my 8 BROADBAND DOUBLE-RIDGE WAVEGUIDE MAGIC TEE The invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Navy.

The present invention relates to magic tee waveguide junctions and more particularly to a double-ridged waveguide magic tee junction.

Conventional magic tee waveguide junctions comprise four rectangular waveguides with two of the waveguides being colinear and forming the side arms and with a third waveguide called the H-arm forming a T-shaped junction with the side arms in the H or magnetic field plane. The fourth arm makes a T-shaped junction with the colinear side arms in the E or the electric field plane and is thus called the E-arm. The E-arm and the H-arm are at right angles from each other. The E-arm is designated as such because it is connected to the colinear arms in the E or electric field plane in a series circuit and the other H-arm is termed as such because it is coupled to the colinear arms in the H or magnetic field plane in a parallel circuit.

In the operation of the magic tee, power delivered to the system at the H-arm will divide equally with equal phase between the colinear arms and no output will be present at the E-arm. Similarly, if power were delivered to the system at the E-arm, no output would be present at the H-arm and the power would divide equally with 180 phase difference in the two colinear arms.

Rectangular waveguides, however, have limited frequency bandwidth where they can be used without the danger of propagating high-order modes. By the placement of a ridge along the waveguide to form what is commonly known as ridge waveguide," the cutoff frequency for the dominant TE mode is lowered sometimes by as much as a factor of five.

A double-ridge waveguide as compared to a single-ridge waveguide for a given range of frequencies, has a different impedance and consequently the power-handling capability of the two types of waveguides is different. The double-ridge waveguide is characterized by a greater power-handling capability compared to that of the single waveguide. Consequently, double-ridge waveguides find wide use in systems where the bandwidths are relatively broad and the power is relatively high.

However, owing to the absence of any known double-ridged hybrid magic tee, the use of a complete, double-ridge waveguide system utilizing magic tees has not been achieved. Double-ridged systems requiring couplings of the magic tee type have heretofore utilized the expedient of connecting a single-ridged hybrid magic tee to the desired double-ridged waveguide sections by an impedance transition section. To provide a minimum of impedance discontinuity between single-ridge waveguides and double-ridge waveguides, a tapered ridge transition section is desirable, if not essential. Such a tapered ridge transition section is made up of a relatively long length of waveguide having a double ridge at one end and a single ridge at the other together with a gradual decrease in the height of one of the ridges along the length of the transition section toward the single-ridge end. Since these above described tapered ridge transition sections must be used on all single-ridge arms of a magic tee, the size and cost of the overall magic tee is greatly increased. In addition, such transition sections effect difficult problems of matching the impedance of the H- and E-arms respectively to the colinear arms.

Since both double-ridge waveguides and single-ridged magic tees have been known for many years, it is believed that a double-ridged magic tee will provide the means to fully utilize a complete double-ridge waveguide system utilizing magic tees. A system as described will cost less and be more efficient than the existing double-ridged waveguide systems which require a single-ridge transition section. It is suggested that perhaps the problem involved in the making of a doubleridged magic tee is that when one attempts to join the upper ridge of the H-arm to the upper ridges of the colinear arms and the E-arm by conventional techniques, the E-arm would be short circuited. According to the present invention, this problem is solved.

It is therefore an object of the present invention to provide a double-ridge magic tee.

Briefly, this object of the present invention is accomplished by at least two rectangular waveguides joined at a common junction to form two colinear arms. A series E-arm is joined perpendicular to both of the colinear anns and is joined at the common junction along the top broad wall of the colinear arms and in the E plane thereof. A parallel l-l-arm is joined perpendicular to said colinear arms and is joined at the common junction along the narrow wall of the colinear arms in the H plane of the colinear arms. Each of the colinear arms, the E- arm and the H-arm have a ridge along both broad walls which extend along the respective lengths thereof. One of the ridges of both of the colinear arms and the H-arm connected to each other at the junction. The other ridge of one colinear arm is connected to a first of the ridges of the E-arrn and the other ridge of the second colinear arm is connected to the second ridge of the E-arm. The other unconnected ridge of the H-arm terminates near the junction with the E-arm. A first conductive member extends between one ridge in the E-arm and said terminated ridge 'of the H-arm. A second conductive member extends between the second ridge in the E-arm and said terminated ridge of the H-arm. The first and second conductive members are spaced from each other by a distance approximately equal to the distance between the ridges of the E-arm.

This invention will be better understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a double-ridge waveguide hybrid magic tee, partially broken to show the point of juncture of the four arms,

FIG. 2 is an elevation view in the plane defined by section lines 2-2, and

FIG. 3 is a plan view in the plane defined by section line 3 3.

Referring to FIG. ll, there is illustrated a double-ridge waveguide magic tee 10 comprising colinear waveguide arms 13 and 15, a waveguide E-arm l7 and a waveguide H-arm 19 joined together at a common region 20. The E-arm 117 extends perpendicular to the broad wall and in the E or electric field plane of the colinear waveguide arms 113 and 15 and is in a series circuit with both colinear arms 13 and 15. The H-arm 19 extends perpendicular to the narrow wall and in the H or magnetic field plane of the colinear waveguide arms 13 and H5 and is in a parallel circuit with these arms 13 and 15. The colinear arm 13 is a rectangular waveguide section loaded by ridges 21 and 23 along the broad walls of the rectangular waveguide 13. Colinear waveguide am 15 is a rectangular waveguide section similarly loaded with ridges 25 and 27. See FIGS. 2 and 3. The E-arm 17 is likewise made up of a rectangular waveguide section loaded by means of ridges 29 and 31 along the broad walls 18 and 22. The H-arm 19 is made: up of a rectangular waveguide having loading ridges 33 and 35 along the broad walls of the rectangular waveguide 19.

Referring to FlGS. ll, 2 and 3, the colinear arms 13 and 15 and the H-arm 19 of the magic tee 10 are arranged such that the ridges 23, 27 and 35 along the bottom broad walls of these arms are connected to each other at the junction 20. The upper ridge 21 of waveguide colinear arm 13 is connected to ridge 31 of the E-arm 17. Similarly, the upper ridge 25 of colinear arm 15 is connected to the ridge 29 of E-arm 17. The upper ridge 33 of the H-arm l9 terminates at the junction 20 and therefore does not extend into the waveguide cross section of the E-arm 17.

A first narrow conductive rod 41 extends parallel to the broad wall 18 of the waveguide of E-arm 17 between ridge 31 of the E-arm and one cross-sectional end 42 of upper ridge 33 of waveguide 19. A second narrow conductive rod 43 extends parallel to the broad wall 22 of the waveguide of E-arm 17 and is coupled between one cross-sectional end 44 of ridge 33 and the ridge 29 of the E-arm 17.

The conductive rods 41 and 43 are spaced from each other by a distance approximately equal to the same distance of the spacing between the ridges 31 and 29. This is accomplished by connecting the rods 41 and 43 at opposite cross-sectional ends of the ridge 33. By the use of these thin conductive rods 41 and 43, the double-ridged hybrid arrangement is sufficiently maintained throughout the magic tee, yet no significant short circuiting of the E-arm occurs, i.e., no significant reflection of RF energy occurs at the E-arm.

Additional RF impedance matching is achieved by the use of a step vane 47 to provide proper impedance transformation between the colinear arms 13-and l5 and the H-arm l9. Vane 47 comprises, for example, three step sections 49, 50 and 51 respectively which behave essentially as three, one-quarter wavelength transformers. The number of steps or construction will depend on the designers choice. Instead of vane 47, irises, rods, tuning screws and such types of successive reactive elements may be so arranged as to provide impedance matching between the colinear E-arms 13 and 15 and the shunt H-arm 19. Improved impedance matching of the series E-arm 17 to the colinear arms 13 and 15 is also provided by capacitive strips 53 and 55. Capacitive strip 53 is coupled to the upper ridge 21 of colinear arm 13 and to ridge 31 of E-arm l7. Capacitive strip 55 is coupled to upper ridge 25 and to ridge 29 of E-arm 17. As mentioned previously, other forms of impedance matching of the series E-arm to the colinear arm may be provided such as that of a tuning screw or post located in the region of the junction of the E-arm and the colinear arms.

In the operation of the arrangement according to the invention, a voltage standing wave ratio (VSWR) ofless than 1.5 to

1.0 across an octave bandwidth over a frequency range between 2 and 4 GHz. (gigaHertz) was achieved.

What is claimed is: 1. A double-ridged magic tee hybrid comprising: at least two colinear rectangular waveguides joined at a common junction to form two colinear arms, a third rectangular waveguide perpendicular to said colinear arms and extending in the E plane of the colinear arms at the junction of said colinear arms to form an E- arm,

a fourth rectangular waveguide arm perpendicular to said colinear arms and extending in the H plane of the colinear arms at the junction of the colinear arms to form an H- arm,

each of the colinear arms, the E-arm and the H-arm. having ridges respectively along both broad walls of the rectangular waveguides which extend along the length of said arm, one of the ridges of both of the colinear arms and one of the ridges of the H-arm being connected to each other at said junction, the other ridge of one colinear arm being connected to a first of the ridges of the E-arm and the other ridge of the second colinear arm being connected to the second ridge of the series E-arm, the unconnected ridge of the H-arm terminating at the junction with the E-arm,

a first conductive member extending between one ridge in the E-arm and the unconnected ridge of the H-arm, and

a second conductive member extending between the second ridge in the E-arm and the unconnected ridge of the H- arm, said first and second conductive members being spaced from each other by a distance approximately equal to the spacing between the ridges of the E-arm.

2. The combination of claim 1 wherein said first and second conductive members are relatively narrow elongated members.

3. The combination of claim I wherein said conductive members extend generally parallel to the broad walls of said E-arm.

4, The combination of claim 3 including a step transformer coupled between said H-arm and said colinear arms.

5. The combination of claim 4 including an impedance matching means positioned between said E-arm and each of said colinear arms.

6. The combination of claim 5 wherein said impedance matching means comprises at least one vane. 

1. A double-ridged magic tee hybrid comprising: at least two colinear rectangular waveguides joined at a common junction to form two colinear arms, a third rectangular waveguide perpendicular to said colinear arms and extending in the E plane of the colinear arms at the junction of said colinear arms to form an E-arm, a fourth rectangular waveguide arm perpendicular to said colinear arms and extending in the H plane of the colinear arms at the junction of the colinear arms to form an H-arm, each of the colinear arms, the E-arm and the H-arm, having ridges respectively along both broad walls of the rectangular waveguides which extend along the length of said arm, one of the ridges of both of the colinear arms and one of the ridges of the H-arm being connected to eacH other at said junction, the other ridge of one colinear arm being connected to a first of the ridges of the E-arm and the other ridge of the second colinear arm being connected to the second ridge of the series E-arm, the unconnected ridge of the H-arm terminating at the junction with the E-arm, a first conductive member extending between one ridge in the Earm and the unconnected ridge of the H-arm, and a second conductive member extending between the second ridge in the E-arm and the unconnected ridge of the H-arm, said first and second conductive members being spaced from each other by a distance approximately equal to the spacing between the ridges of the E-arm.
 2. The combination of claim 1 wherein said first and second conductive members are relatively narrow elongated members.
 3. The combination of claim 1 wherein said conductive members extend generally parallel to the broad walls of said E-arm.
 4. The combination of claim 3 including a step transformer coupled between said H-arm and said colinear arms.
 5. The combination of claim 4 including an impedance matching means positioned between said E-arm and each of said colinear arms.
 6. The combination of claim 5 wherein said impedance matching means comprises at least one vane. 